Drive control method of electrostatic-type ultrasonic transducer, electrostatic-type ultrasonic transducer, ultrasonic speaker using electrostatic-type ultrasonic transducer, audio signal reproducing method, superdirectional acoustic system, and display

Abstract

A push-pull-type electrostatic-type ultrasonic transducer includes a first electrode having through holes, a second electrode having through holes each of which is paired with the corresponding through hole of the first electrode, and an oscillation film sandwiched between a pair of the first and second electrodes and having a conductive layer to which direct current bias voltage is applied. When a wavelength obtained from a resonance frequency at a mechanical oscillation resonance point of the oscillation film is λ, a thickness t of the respective fixed electrodes is (λ/4)·n or substantially (λ/4)·n (where λ: wavelength of ultrasonic wave, n: positive odd number). AC signals as modulation waves produced by modulating carrier waves in an ultrasonic frequency band by signal waves in an audio frequency band are applied between a pair of the electrodes.

1 . An electrostatic-type speaker, comprising:
 a first electrode having a plurality of through holes,   a first insulation layer on the first electrode,   a conductive layer on the first insulation layer,   a second insulation layer on the conductive layer,   a second electrode on the second insulation layer, the second electrode having a plurality of through holes,   wherein mutually phase-inverted signals are applied to both the first electrode and the second electrode.   
     
     
         2 . The electrostatic-type speaker according to  claim 1 ,
 wherein the conductive layer receives forces from the first electrode and the second electrode and oscillates.